qgisscale-factorzoom
I have a map project with CRS = NAD83 zone 13N. The canvas will zoom to 1:144,447, 1:288,295, 1:577,790, etc. The values in the dropdown, on the other hand are 1:100,000, 1:250,000, 1:500,000, etc. Why is it zooming to these odd values and how do I coerce it to zoom to the levels in the dropdown or typed into the scale box?
QGIS 2.12.1 – Lyon
Win 7 Pro 64 bit
You need to uninstall 'Tile Map Scale Plugin' :) If you don't have this plugin installed, perhaps the same problem can be caused by another plugin, so try uninstalling all plugins and see if that fixes the problem.
As far as I understand from the discussion on the comments, what you want to do is to generate an image of a large area, which is so big that does not fit on your screen and, hence, you have to zoom out, resulting in a loss of detail.
In order to export large areas, you may want to use QGIS' built-in Print Composer, this way you can control map's scale (which, as @Andrej stated, you can figure out which scale level has the detail you want to).
After that, you can export the image into a Raster or vector format, and most importantly, you won't be limited by your screen's size or resolution, as you can choose the image's resolution and dpi.
The summarised process would be as follows:
Project\New Print Composer (CTRL+P) Give
your composition a name (it can be anything) Composition tab). That will be your canvas.![![enter image description here]](https://i.stack.imgur.com/m2ht2.png){kind=link}
Item properties tab) 
) or export to svg icon (
).
Best Answer
QGIS usually zooms to the layer extent after loading. By using the mousewheel, you can then zoom by a factor of 2. Selecting a different value in the scale dropdownbox will change the current value.
If you have installed the
Tile Map Scalesplugin, scales will be set to an optimal view for EPSG:3857 based tile servers, like OpenStreetMap or Google. in theoptionstab of the plugin, you can uncheckUse World Mercator Systemto get free scale levels back.